Thermal processing equipment, such as ovens and furnaces, used in the heat treatment of materials are subject to very tight temperature tolerances, especially as applied to aerospace materials. Precise calibration and accurate correction factors are, therefore, critical in this field. Procedures for ascertaining the accuracy and uniformity of furnace temperature controls are established by engineering/technical standards, such as those issued by SAE International. One example of such standards is the SAE Pyrometry Aerospace Material Specification, the current version of which is AMS2750E. The AMS2750E standard addresses, among other things, procedures for conducting a System Accuracy Test (SAT) and a Temperature Uniformity Survey (TUS). The SAT measures the accuracy of a chamber, oven or furnace temperature control system(s) (Controller/Recorder/High Limit Safety, etc., thermocouple extension wire and thermocouple), while the TUS measures temperature variations within a furnace prior to and after temperature stabilization.
Entities which perform pyrometry testing, such as SAT and TUS, may choose to be ISO/IEC 17025 accredited, which provides them with third party validation in assuring the quality of their calibration and testing activities. Such accreditation requires, among other things participation in proficiency testing, interlaboratory comparisons or round robbins in which one or more pyrometric test(s) are performed and deviations between temperature readings and true temperatures are recorded. Requirements for such proficiency testing are established by bodies such as the Laboratory Accreditation Bureau (L-A-B), A2LA, NVLAP, etc.
One of the principal purposes of pyrometric proficiency testing is to demonstrate the ability of each participant to accurately measure temperature and to provide measurements of uncertainty associated with those measurements. This would be problematic when performing system accuracy tests or temperature uniformity surveys unless each participant was able to use the same thermal processing equipment. The present invention addresses this problem by providing a compact, portable heating chamber for pyrometric proficiency testing, which can be readily transported between different laboratory environments and used with different test instrumentation and/or data acquisition devices to determine each participant's ability to make accurate measurements and to qualify those measurements by stating the associated uncertainties of each measurement.